A major purpose of the dental profession has been to replace or correct damaged or deformed tooth structure or conditions by fabricating and installing dental constructs such as crowns, inlays, onlays, bridges (fixed partial dentures) and the like. These prostheses ideally should (1) be inert in the oral environment, (2) resist the forces of mastication, (3) be capable of assuming physiologically compatible anatomical configurations, and (4) exhibit aesthetic characteristics similar to those of natural teeth.
Present dental constructs are customarily composed of metal alloys, porcelain, amalgam, or acrylate polymers or combinations thereof, which do not completely meet the foregoing ideal requirements. Metal alloys and amalgam are undesirable in locations where aesthetics is a major consideration because they sharply differ from teeth in optical characteristics. Porcelain and acrylate polymers are either too brittle or too weak to resist masticatory forces in many locations. Composite structures, as in the case of an alloy substructure for strength and a porcelain superstructure for appearance are generally very technique sensitive and many times are very bulky. Therefore, prior dental constructs have been at best a compromise upon the four ideal requirements.
One drawback especially with the constructs employing metal alloys, is that these often release potentially toxic ions such as those from nickel in the base metal alloys. Another area with previous dental constructs have been deficient is in the ease of customizing shade and aesthetics of the material and matching the patient's existing dentition. Ceramic crowns have normally required greater involvement between the dental practitioner and the dental laboratory in order to adequately customize the shade and aesthetics. It has also been a problem that ceramic veneers are subject to fracture. A further problem encountered with the metal-ceramic veneered system is fracture of the ceramic veneer. Such a problem inevitably requires the expensive and complicated procedure of removal of the crown or bridge from the mouth in order for it to be repaired or remade by the dental laboratory. In this regard, it has been found that the greater the difference between the thermal expansion qualities of metal and that of the ceramic materials applied thereto with previous constructs, aggravate the problem of cracking or fissuring. Such problems become increasingly troublesome with the number of re-firing schedules of the ceramic-metal construct.
A need exists therefore, for a dental construct having ease of manufacture qualities. A need also exists for such a construct having improved aesthetic characteristics and biocompatability. The constructs should be easily customized for colour shading and shape at the chair-side. In order to avoid delamination of the veneering material, the substrate and the veneering material of a dental construct should ideally not be sensitive to slight mismatch between their thermal expansion characteristics. In addition the veneering material should not be subject to failure at very low strains.